During early embryogenesis in all vertebrates, bilateral symmetry is broken to give rise to the embryonic Left-Right axis. LR information is transmitted to a wide variety of developing organ primordia, including the heart. Although significant advances have been made in our understanding of a complex set of pathways that control intermediate steps in LR development, the genes, molecular and cellular mechanisms responsible for the initiation of the LR axis are unknown. Syndecan-2 is a single-pass transmembrane heparan sulfate proteoglycan. We recently found that one of the earliest steps in LR development is mediated through Protein Kinase C gamma (PKCgamma)-dependent asymmetric phosphorylation of Syndecan-2. This initiates a novel "inside-out" signaling pathway, in which asymmetrically phosphorylated Syndecan-2 transduces LR information from ectoderm cells to migrating mesoderm cells during early gastrulation. The research in this proposal will elucidate the molecular pathways that initiate LR asymmetry in syndecan function and the mechanisms by which syndecan-2 can send at least two distinct signals (left or right) to migratory cells. Besides LR development, the proposed research will elucidate two other roles for syndecan-2: it regulates fibronectin fibrillogenesis, by forming a signaling complex with PINCH and integrin, and it is capable of re-orienting the direction of migrating mesoderm cells. The long-term goal of this research is to significantly increase our understanding of the genes and mechanisms that control cardiovascular development, cell-cell signaling, extracellular matrix formation, and cell migration. The principles derived from this research will be applicable to a wide range of cell-cell signaling events in development and disease.